The invention relates to a one-piece component as well as to a method for its manufacture, more particularly for fixing on a crankshaft of an internal combustion engine wherein the component has at least one axially formed mounting for a ring-shaped component which is to be attached centred at a later time, the component is made by means of a cold forming process and the component has in the area of the mounting surface a radially formed stop shoulder.
Components of this kind are described many times in prior art and normally represent a flywheel mass which is fixed on the crankshaft, with an axial seat onto which a starter ring gear is drawn, with a radially aligned stop shoulder. To ensure centring of the starter ring gear the centred mounting is formed by removing some stock material. This leads to an increase in the manufacturing costs and production times since the component has to be mounted in various machines and processed.
The object of the invention is therefore to provide a cost-effective and correspondingly simple to manufacture component as well as a manufacturing method suitable for this where the component is made without stock removal.
This is achieved in that a one-piece component is made by means of a cold forming process with an axially oriented mounting surface for subsequent attachment and centring in position of a ring-shaped component, and a radially oriented shoulder formed from a material accumulation formed radially outside during forming of the axially oriented mounting surface.
The axial mounting surface can be formed by at least one and preferably several circumferentially spaced circular recesses or circumferentially through the formation of a ring-shaped mounting surface. Consequently the radially designed stop shoulder can also be made from individual material thickenings or accumulations in the radial direction spread out over the circumference or can form a substantially circumferential stop. At certain angular regions of the shoulder circumference which are subject to additional imprinting steps before or after the method of the invention, the formation of the stop shoulders can be omitted through a lack of material. Preferably a starter ring gear and/or ignition marker ring is drawn onto the resulting contact bearing surface and this ring can then be welded, caulked and/or shrink-fitted thereon.
It can equally be advantageous to provide corresponding contact bearing surfaces in addition or as an alternative for mounting a flywheel mass or a bearing, such as for example a rolling or sliding bearing, for mounting a flywheel mass on the component. It can also be advantageous to provide a contact bearing surface for the centred fitting of the crankshaft.
To fix the ring-shaped component on the contact bearing face so that it is secure against tilting it can be advantageous to make the axial dimension of the mounting surface at least half the axial dimension of the ring-shaped component which can be attached so that it can be possible to fix the ring-shaped component by press-fit onto the contact bearing face of the one-piece component without further connection measures such as for example welding.
Further advantageous developments of the one-piece component can be for example a flywheel to be fixed on the crankshaft or an axially elastic and circumferentially rigid drive plate as well as a flywheel disc part of a divided flywheel.
Thus for example the one-piece component can be a primary part with a flywheel mass and this primary part can be rotated relatively against at least one secondary part which can be connected for engagement and disengagement with a gear input shaft having a flywheel mass, against the action of a damping device acting at least in the circumferential direction in the force flow between the primary and secondary part. In an advantageous development the one-piece component then forms the complete primary flywheel disc part of the divided flywheel or in a further advantageous embodiment only the bearing flange which is connected to the crankshaft through the centred bearing face. The primary flywheel disc part can then be connected to the bearing flange by means of rivets for simple assembly and to reduce the number of rivets.
Axially formed nipples can be imprinted by the cold forming technique in one of the two parts which are to be riveted and the nipples can engage in corresponding openings in the other part and be riveted at their end sides to the edges of the openings. Through the high forces which occur during the riveting process it may happen that the centring of the bearing flange provided in the bearing flange for mounting on the crankshaft becomes impaired, for example compressed.
It is therefore advantageous to provide the openings in the bearing flange and the nipples in the flywheel disc part and to design the openings so that at least three noses are formed evenly spread out over the inner circumference of the openings and aligned radially inwards with the nipples provided in the primary flywheel disc being riveted to the noses. Advantageously the alignment of the noses is such that none of the noses is mounted on an imaginary line between each centre of the openings and the axis of rotation of the bearing flange so that in this area of the centring of the contact bearing face lying closest no compression forces appear with the material flow in the direction of the centring during riveting and thus the centring can be properly maintained.
A further advantageous embodiment of the one-piece component has, when used in a divided flywheel, the provision of a transport retaining lock wherein the primary flywheel disc part is fixed secured against rotation relative to the secondary flywheel disc part during transport or assembly.
Advantageously the transport retaining lock is placed radially between circumferentially arranged energy accumulators belonging to the damping device, and a mounting of the primary flywheel disc part on the crankshaft. Advantageously the transport retaining lock can consist of a plastics part which is snap-fitted in correspondingly recessed window-shaped openings in the primary and secondary flywheel disc parts and has a designed in break point axially between the primary and secondary flywheel disc parts.
The openings are in particular punched out in the one-piece component according to the invention which functions as a primary disc part.
Furthermore it can be advantageous to snap-fit the transport retaining lock in the form of the plastics part into a corresponding opening of a radially aligned flange part connected rotationally secured to the secondary flywheel part for biasing the energy accumulators on the secondary side and into the primary flywheel disc part. The transport retaining lock is advantageously dimensioned so that it separates completely with the initial start-up of the internal combustion engine.
In a divided flywheel having the one-piece component according to the invention this can be formed as a primary flywheel disc part so that at least one radially inwardly open chamber adapted in the circumferential direction to the extent of the energy accumulators is formed on the outer circumference out of the primary disc part and/or in connection with at least one component connected thereto. The flange part connected rotationally secured to the secondary flywheel disc part engages from radially inside through the chamber for biasing the energy accumulators with the energy accumulators housed in the chamber and the chamber being filled at least in part with lubricant for lubricating the energy accumulators.
Furthermore it can be advantageous to provide, radially inside the inner circumference of the chamber, punched-out assembly and/or ventilation bores spread out around the circumference and having a raised punched aperture whereby lubricant which may be warmed up and which during stationary periods of the crankshaft is forced radially inwards is supplied back along the profiled aperture through centrifugal force into the chamber during subsequent rotation of the crankshaft and does not pass radially inwards onto the friction device which is provided radially outside of the bearing which mounts the two flywheel disc parts on one another.
A further advantageous development of the one-piece component for use as a primary flywheel disc part can be the stamping of the primary disc part to a centring diameter on which a ring-shaped component such as for example the ignition marking ring, can be centred and mounted, and in a simplified method of assembly can be connected for example welded to the primary flywheel disc part or a component connected thereto, such as for example the flange forming the chamber. It can also be advantageous here to make the punched aperture of the centring diameter raised in order to obtain radial play for any welded seams which may be provided between the primary disc part and a radial flange part, by way of example for forming the chamber.
More advantageously an ignition marking ring which is to be fitted round the outer circumference of the primary flywheel part is likewise made by cold forming technology and is punched out from a round plate. In order to obtain internal stability and additional mass the ring can be folded at least once in the radial direction and may have on the outer circumference an axially aligned ring face in which the ignition markings are provided in the form of a chamber or window structure.
The one-piece component described in various forms above can be made by the advantageous method described below for manufacturing the one piece component without stock removal wherein the method is divided up into at least the following method steps:
1. A three-dimensional preform having at least one axial ring face is made from an approximately planar plate of cold deformable material such as steel by the cold forming process;
2. The preform is centred, for which the preform is correspondingly prepared, by way of example centring cams and the like can be imprinted therein onto which the blank shape is mounted;
3. In a method step at least one axial contact bearing face is formed on the axial ring face for centring a ring-shaped component which is to be attached at a later time, and from the material which is displaced in the axial direction as the contact bearing face is formed, a radially designed stop shoulder is formed by a cross flow process.
4. A tool required for the process can be designed so that the contact bearing face is shaped circumferentially or partially spread over the circumference, by way of example in the form of three contact bearing faces spread out over the circumference. It follows from this that the stop shoulder is correspondingly shaped out, namely either circumferentially or in the form of stop cams spread out over the circumference.
5. In a following method step apertures can be punched out and/or studs, by way of example axially formed nipples, are imprinted for forming the rivet connections with a component which is to be attached.
A further advantageous development of the method is a method step wherein holes are punched out which have a raised punched aperture. Holes or openings of this kind can serve for example for ventilation or as assembly access whereby the raised punched aperture can have advantages, as already described. Furthermore it can be advantageous to punch out the entire one-piece component centred and also here to provide a raised punched aperture in order to fit a further component on the centred diameter and to create a gap through the raised punched aperture radially between the additional component and the one-piece component which can be occupied for example by a welded seam with which the one-piece component is connected to a further axially adjoining component.
A further advantageous embodiment allows the one piece component to undergo following the process according to the invention a hardening process whereby hardened parts such as for example the bearing flange can be made without stock removal and without additional calibrating processes.
The invention will now be explained in further detail with reference to the drawings in which: